1. Field of the Invention
The present invention relates to a microfluidic chip for steam distillation and, more particularly, to a microfluidic chip for steam distillation useful in analyzing micro sample solutions.
2. Description of the Related Art
Methanol (HCHO) is a colorless, soluble gas that can be absorbed by a human body via the respiratory tract. It turns into formalin (the concentration is about 30-40%) when it dissolves in water and can be absorbed by the human body via the gastrointestinal tract.
Since methanol provides functions including bleaching, enhancing coagulation of protein, and preserving freshness, many unscrupulous businessmen maliciously added methanol into foods. After absorption by the human body, methanol will combine with the amino terminal of protein and cause denaturation of protein, damaging normal functions of the cells of the human body. Thus, detection of methanol in foods is an inevitable process for assuring food safety.
Steam distillation is one of the methods for separating a liquid from a solid and is suitable to extract volatile ingredients that can not be damaged by high temperature steam, that do not react with water, and that are difficult to dissolve in water or insoluble to water. Thus, current detection of methanol content in foods includes extraction of methanol by steam distillation and subsequent calculation of the methanol content by titration of sodium thiosulfate solution.
FIG. 1 shows a conventional steam distillation device 9 including a steam generating flask 91, a sample flask 92, and a condenser 93. The steam distillation device 9 further includes a steam guiding tube 94 and a sample guiding tube 95. The steam guiding tube 94 is connected to the steam generating flask 91 and the sample flask 92. The sample guiding tube 95 is connected to the sample flask 92 and the condenser 93. The steam generating flask 91 generates high temperature steam that flows through the steam guiding tube 94 into the sample flask 92 receiving a sample solution S. A volatile substance (such as methanol) contained in the sample solution S evaporates into a gaseous analyte. The gaseous analyte flows along the sample guiding tube 95 into the condenser 93 and condenses into a liquid analyte. Thus, the volatile substance (i.e., the liquid analyte) can be extracted from the sample solution S and can be detected to obtain its content.
However, the sample flask 92 used in the conventional steam distillation device 9 is generally a 250 mL conical bottle which is not suitable for receiving a difficult-to-obtain sample solution S of only about 0.2-0.5 g in a single use. Furthermore, assembly of the bulky condenser 93 is required, leading to a bulky steam distillation device 9 as well as difficulties in storage.